GCSE Biology, Paper 1, Combined (Triology/Higher): Cell Biology, Organisation, Infection and Response, and Bioenergetics

Comprehensive practice flashcards covering Cell Biology, Organisation, Infection and Response, and Bioenergetics.

How does the genetic material in a prokaryotic cell differ from that in a eukaryotic cell?

In eukaryotic cells, genetic material is enclosed in a nucleus. In prokaryotic cells, the genetic material is not enclosed in a nucleus; it is a single DNA loop and there may be one or more small rings of DNA called plasmids.

What are the functions of the mitochondria and ribosomes in animal cells?

Mitochondria release energy by respiration, and ribosomes are the sites of protein synthesis.

What formula is used to calculate magnification?

$$\text{magnification} = \frac{\text{measured size}}{\text{actual size}}$$

What events occur during the cell cycle before a cell divides by mitosis?

The cell grows and increases the number of sub-cellular structures such as ribosomes and mitochondria, and the DNA replicates to form two copies of each chromosome.

What is a stem cell, and what differentiation capability does plant meristem tissue have?

A stem cell is an undifferentiated cell capable of giving rise to many more cells of the same type and differentiating into certain other cell types. Meristem tissue in plants can differentiate into any type of plant cell throughout the life of the plant.

What is therapeutic cloning, and what is its primary medical benefit?

An embryo is produced with the same genes as the patient, meaning stem cells from the embryo are not rejected by the patient's body and can be used for medical treatment.

What is diffusion, and what three factors affect its rate?

Diffusion is the spreading out of particles of any substance in solution or gas, resulting in a net movement from an area of higher concentration to an area of lower concentration. Its rate is affected by the concentration gradient, the temperature, and the surface area of the membrane.

What is osmosis?

Osmosis is the diffusion of water from a dilute solution to a concentrated solution (or from a high water concentration to a low water concentration) through a partially permeable membrane.

How does active transport differ from diffusion regarding concentration gradients and energy requirements?

Active transport moves substances from a more dilute solution to a more concentrated solution (against a concentration gradient), which requires energy from respiration.

How is a tissue defined compared to an organ?

A tissue is a group of cells with a similar structure and function, whereas an organ is made up of a number of tissues that work together to perform a specific function.

Where is bile produced, where is it stored, and what are its two digestive roles?

Bile is made in the liver and stored in the gall bladder. It is alkaline to neutralise hydrochloric acid from the stomach, and it emulsifies fat into small droplets to increase surface area for lipase activity.

Which enzyme breaks down carbohydrates into simple sugars, and where is amylase produced?

Carbohydrase breaks down carbohydrates into simple sugars. Amylase is produced in the salivary glands, pancreas, and small intestine.

What are the substrate and end products for protease and lipase enzymes?

Protease breaks down protein into amino acids. Lipase breaks down lipids (fats) into fatty acids and glycerol.

What chemical solutions are used to test for glucose, starch, and protein, and what are their positive results?

Benedict's solution tests for sugars/glucose (positive result: green, orange, red); iodine solution tests for starch (positive result: blue/black); Biuret solution tests for protein (positive result: violet).

How do the destinations of blood pumped by the right and left ventricles differ?

The right ventricle pumps blood to the lungs where gas exchange takes place, while the left ventricle pumps blood around the whole body.

How do arteries and veins differ in structure, blood pressure, and direction of blood flow?

Arteries carry blood away from the heart under high pressure and have thick muscular walls. Veins carry blood to the heart under low pressure, have thin walls, and possess valves to prevent blood flowing backwards.

What are the four components of blood, and what is the specific role of platelets?

Blood is composed of plasma, red blood cells, white blood cells, and platelets. Platelets help the blood to clot, forming a scab.

What happens in coronary heart disease (CHD), and how do stents and statins treat it?

Layers of fatty material build up inside the coronary arteries, narrowing them and reducing blood flow and oxygen to the heart muscle. Stents keep the coronary arteries open, while statins reduce blood cholesterol levels to slow down fatty deposit formation.

How does a benign tumour differ from a malignant tumour?

A benign tumour is a growth of abnormal cells contained in one area that does not invade other parts of the body. A malignant tumour consists of cancer cells that invade neighbouring tissues and spread through the bloodstream to form secondary tumours.

What structural feature of xylem adapts it for water transport, and what is the transport process in phloem called?

Xylem is composed of hollow tubes strengthened by lignin for the transpiration stream. The movement of food molecules/dissolved sugars through phloem tissue is called translocation.

How are spongy mesophyll cells adapted to facilitate photosynthesis?

Spongy mesophyll contains air spaces between cells to provide a large surface area for carbon dioxide to diffuse through and reach the palisade cells.

Which four environmental factors affect the rate of transpiration?

Temperature, humidity, air movement, and light intensity.

What pathogen causes Salmonella food poisoning, how is it controlled in poultry, and what are its symptoms?

Salmonella is caused by bacteria. Poultry are vaccinated against it to reduce disease spread. Symptoms include stomach cramps, fever, vomiting, and diarrhoea.

How does Tobacco Mosaic Virus (TMV) affect plant development?

TMV causes a 'mosaic' pattern of discolouration on leaves, which reduces the plant's ability to photosynthesise and therefore grow.

By what three methods do white blood cells defend the human body against pathogens?

They ingest/engulf pathogens (phagocytosis), produce antibodies that kill specific pathogens, and produce antitoxins that counteract toxins released by pathogens.

Why can antibiotics treat bacterial infections but not viral infections?

Antibiotics kill bacteria only and cannot kill viruses because viruses live and reproduce inside host cells, where antibiotics are unable to reach them.

From which biological organisms were digitalis, aspirin, and penicillin originally discovered?

Digitalis originates from foxgloves, aspirin comes from willow, and penicillin was extracted from the fungus Penicillium by Alexander Fleming.

What are the cohort sizes and primary objectives of Phase I, II, and III clinical human drug trials?

Phase I uses a small group ($20$ to $100$) of healthy volunteers given a very low dose to check for safety/side effects. Phase II tests $200$ to $400$ volunteer patients to evaluate effectiveness. Phase III tests over $3000$ volunteer patients to confirm effectiveness and find the safest dose.

What is the distinction between a blind trial and a double blind trial?

In a blind trial, patients do not know whether they have been given the active drug or a placebo. In a double blind trial, neither the patients nor the doctors know who has received the drug or the placebo.

What is the balanced symbol equation for photosynthesis?

$$6CO_2 + 6H_2O \rightarrow C_6H_{12}O_6 + 6O_2$$

How does doubling the distance of a light source affect light intensity according to the inverse square law?

Doubling the distance quarters the light intensity ($\text{intensity} \propto \frac{1}{d^2}$).

What are five distinct ways plants utilise the glucose produced by photosynthesis?

Plants use glucose for aerobic respiration, convert it into insoluble starch for storage, use it to produce fat or oil for storage, make cellulose to strengthen cell walls, and combine it with nitrate ions to produce amino acids for protein synthesis.

What is the chemical equation for anaerobic respiration in muscles, and why does it yield less energy than aerobic respiration?

$C_6H_{12}O_6 \rightarrow 2C_3H_6O_3 + \text{energy}$. Much less energy is transferred because the oxidation of glucose is incomplete.

What is the balanced symbol equation for anaerobic respiration in yeast cells (fermentation)?

$$C_6H_{12}O_6 \rightarrow 2C_2H_5OH + 2CO_2 + \text{energy}$$

What is oxygen debt?

Oxygen debt is the amount of extra oxygen the body needs after exercise to react with the accumulated lactic acid and remove it from the cells.

What is metabolism, and what synthesis reactions does it include?

Metabolism is the sum of all chemical reactions in a cell or the body. It includes converting glucose to starch, glycogen, and cellulose; forming lipid molecules from $1$ molecule of glycerol and $3$ molecules of fatty acids; and using glucose and nitrate ions to form amino acids for protein synthesis.